In the field of military transport airplanes, aircraft are known that have main undercarriages fastened to a side structure of the fuselage, such as for example the C160 Transall or the A400M. In general, main undercarriages are arranged on either side of the fuselage, and on each side they are arranged one behind another. In general, each undercarriage has a rocker beam with one end that receives an axle carrying two wheels. The rocker beam is hinged about a transverse axis, either to a leg of the undercarriage, or else directly to a structure that is secured to the fuselage. Under such circumstances, a retraction device pulls on the shock absorber connected to the rocker beam in order to turn it towards a retracted position in which the rocker beam and the wheels are received inside a lateral fairing of the fuselage.
Wing undercarriages are also known comprising a leg that is hinged under the wing about a hinge axis, with the bottom end of the leg carrying a pivot on which there are hinged two rocker beams each carrying an axle, one of the rocker beams extending forwards and the other of the rocker beams extending rearwards, e.g. as in the Caravelle or Nimrod airplanes. The undercarriage includes a shock absorber device comprising two connecting rods coupled to respective ones of the rocker beams, at least one of the connecting rods being telescopic and forming a shock absorber, the two connecting rods also being coupled to a rocker that is pivotally mounted on a pivot of the leg of the undercarriage. The assembly is pivotable as a whole about the hinge axis of the leg in order to be a retracted into the structure of the aircraft.